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I drilled 2 of my 3 holes this past weekend. I could not tell you how scared I was drilling the first hole. Once I started it was super easy. I had 2 holes done in less than 30 minutes with lots of "stop and take a look" time.

I will be getting the hole saw for the 3rd hole this week!!

Major thanks to JustOneMoreTank for posting this and giving me the blind confidense I needed, so that that I too could do this.

__________________
Chris

My son said I should have been a potato bug farmer.
Pickles are cucumbers soaked in EVIL!!

Check out Marine Depot to figure out the size hole necessary for what size BulkHead you are planning on using... they make it easy for you because it is listed.
You may have to convert the inches to millimeters in order to buy the correct hole saw. http://www.marinedepot.com/aquarium_...tings_2.asp#bh

Originally posted by H20ENG Glad you did not use antifreeze.
Many people have misconceptions that antifreeze causes the water to be more heat conductive, or will magically cool itself. Pure water is the best coolant and heat transfer fluid- which is why every other materials specific heat is compared to that of water- which is 1.0.
Antifreeze is used for just that purpose- to lower the freezing temperature of the water (mix). It actually hampers its heat carrying capacity a bit, but that is the tradeoff for being able to not freeze up in cold weather.

I believe the intended use of antifreeze was not necessarily only for heat transfer but also for its' lubricating properties. However, it is a poisonous substance that needs to be disposed of properly and I would not use it. Glass shops use it diluted along with diamond grit/dust to make a slurry as they drill. The bits that many older glass shops use are not diamond encrusted, they are copper tube type and use the diamond grit to grind through the glass. These bits last forever, my local shop has had their bits for over 40 years! And, they drill some thiiiiick glass for commercial uses (banks, etc).

I'm contemplating how I'm going to drill my brand new Oceanic 30g cube, I want a Calfo style overflow but don't know if I should drill holes or a slot in the back for an external overflow box. I will also have a single hole for a CL.

Originally posted by causeofhim Thanks for giving me the guts to try it out.

No problem. Did you finish the job or have you just got up the courage to start the drilling this weekend. Be sure to take some pictures and show everyone here on this thread. We would all like to see your results.

I have been thinking of using a 8mm or 6mm bit to drill a number of holes/slots to be used to create an external overflow on a tank. Anyone see a problem with doing it this way? The dremel method seems like it would be a real pain to etch out all the slots, and the drill bit would at least give nice clean circles.

FWIW, a glass cutting company published that you should not exceed something like 200RPMs when drilling glass with a diamond hole saw. i can't recall why, but that's what i did. very slowly and hardly any pressure. i was too affraid of cracking my new 55g tank. 3 holes went nice just that the hole saws werent 100% true. they wobbled a bit. i even bought a new drill of a different brand and corded, and it still wobbled. oh well.

You don't want "slots" for an overflow. This has to be one of the most useless "fads" or "trends" in reef keeping. The only time slots are usefull is when the linear overflow length is to short and the water going over the falls is 1/4" or more deep. Making a wider overflow is the solution, then teeth will not be needed to keep critters out.

ANy time you add teeth, you diminish the surface skimming ability of the overflow. If it is already to narrow and teeth are needed to keep out the critters, then all the teeth will do is make that much worse! In conlcusion, teeth should nerver be used, as they defeat ther purpose of a linear style overflow.

I'm certainly not trying to be argumentative, but I do not see why slots/teeth in an overflow diminish skimming ability? If I id not have teeth, and have a 12" wide opening for the water to flow, this would be the same as having a 1/2" opening every inch for 24 inches. Exact same area for water to flow, only the teeth will keep my fish (my wrasse and hawkfish are jumpers) out and keep snails, etc out. Fishing my wrasse out of my overflow really is not a fun task!